Revert "Implementation of tags collection API through use case, refs T238"

This reverts commit 18a592fa79a953d19521b94a87e29d8225e6e7f0.

It keeps the new `_get_paging_parameters()` method in API base controller.

Conflicts:
	application/classes/Controller/Api/Tags.php
	application/classes/Ushahidi/Formatter/API.php
	src/Ushahidi/Tool/Formatter.php